The present invention relates to a photo-sensor used in a portable equipment such as a portable telephone, remote controller and others, and to a method for manufacturing the photo-sensor.
The remote controller is used for controlling the operation of an electronic equipment such as an audio-visual equipment and a communication equipment, by using infrared rays and visible rays. On the other hand, the equipment controlled by the signal rays from the remote controller is provided with a photo-sensor having a light-sensitive element such as a photodiode or a phototransistor for detecting the control signal.
The conventional photo-sensor can not detect signal rays which is not sensed by the spectral responsivity of the light-sensitive element mounted on the photo-sensor.
Japanese Patent Application Laid Open 08-204653 discloses a photo-sensor. The light-sensitive element provided in the photo-sensor is coated with an epoxy resin mixed with a visible light protective agent so that a condenser lens is formed on the photo-detector constructed with an engineering plastic containing an infrared ray protective agent as an optical band pass filter.
Japanese Patent Application Laid Open 10-223039 discloses another photo-sensor provided with a light-sensitive element. The photo-sensor has a band pass filter with an interference film having a transmission central wavelength approximately coincident with a central wavelength of signal rays from a remote controller.
FIG. 4 is a graph showing a spectral responsivity of a conventional photo-sensor. In the graph, the reference a shows an inherent spectral responsivity of the light-sensitive element, and the reference b shows a spectral responsivity of a photo-sensor having a band pass filter.
However, in a visible ray sensor, particularly a luminous efficiency sensor, a light-sensitive element which is a band pass filter element having a luminous efficiency had to be used. In order to provide a band pass function in the light-sensitive element to be used, a dielectric multilayer or a metal multilayer is formed on a light receiving portion by evaporation.
Another method is to form an absorption layer on the light-sensitive element or to add an impurity to the light-sensitive element, thereby controlling the band to improve the epitaxy construction.
These methods increase the manufacturing cost. Furthermore, it is difficult to control the filtering effect of the light-sensitive element, and hence there is limit to improve the band pass filtering effect. If an outside filter is used, the photo-sensor is increased in size and the manufacturing cost rises.